java如何在JTextArea中保存编辑过的文本文件？

Question

我正在尝试用Java编写一个文本编辑器应用程序。下面的程序读入一个文本文件，然后通过BufferedReader方法显示它。然而，在这一点上，我完全被卡住了。可以在JFrame窗口中编辑显示的文本。但在编辑之后，我不知道如何关闭并保存已编辑的文件（即如何合并事件处理程序，然后保存已编辑的文本）

我已经尝试了很多事情，但是我非常感谢你能帮助我从这一点上取得进展。我对Java非常陌生，所以可能我的程序的整个结构都是错误的-非常感谢任何帮助。主程序在这里，后面是它调用的显示面板创建者。程序应该弹出一个窗口，其中包含您已放置在目录中的名为text.txt的任何文本文件

主要内容：

import java.io.*;
import java.util.ArrayList;
import static java.lang.System.out;
public class testApp4 {
    public static void main(String args[]) {
        ArrayList<String> listToSend = new ArrayList<String>();
        String file = "text.txt";
        try (BufferedReader br = new BufferedReader(new FileReader(file))) 
        {
            String line;
            while ((line = br.readLine()) != null) {
               listToSend.add(line);
            }
        br.close();
        }
        catch(FileNotFoundException e)
        {
            out.println("Cannot find the specified file...");
        }
        catch(IOException i)
        {
            out.println("Cannot read file...");
        }
        new DisplayPanel(listToSend);
    }
}

显示面板创建者：

import java.awt.Font;
import java.util.ArrayList;
import javax.swing.JFrame;// javax.swing.*;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JScrollPane;
import javax.swing.ScrollPaneConstants;

public class DisplayPanel {
    public DisplayPanel(ArrayList<String> list) //constructor of the DisplayGuiHelp object that has the list passed to it on creation
    {
        JTextArea theText = new JTextArea(46,120); //120 monospaced chrs
        theText.setFont(new Font("monospaced", Font.PLAIN, 14));
        theText.setLineWrap(true);
        theText.setEditable(true);
        for(String text : list)
        {
            theText.append(text + "\n"); //append the contents of the array list to the text area
        }
        JScrollPane scroll = new JScrollPane(theText);
        scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

        JPanel mainPanel = new JPanel();
        mainPanel.add(scroll);

        final JFrame theFrame = new JFrame();
        theFrame.setTitle("textTastico");
        theFrame.setSize(1100, 1000);
        theFrame.setLocation(550, 25);
        theFrame.add(mainPanel); //add the panel to the frame
        theFrame.setVisible(true);

        System.out.print(theText.getText()); //double check output!!!

    }
}

Answer 1

处理此问题的一种方法是更改窗口关闭的默认行为，并添加一个WindowListener，用于捕获窗口关闭事件并在那里进行保存

可以添加到DisplayPanel类中的一个简单示例（在创建jFrame对象之后）：

    theFrame.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
    theFrame.addWindowListener(new WindowAdapter() {
        @Override
        public void windowClosing(WindowEvent e) {
            super.windowClosing(e);
            String[] lines = theText.getText().split("\\n");
            try (BufferedWriter writer = new BufferedWriter(new FileWriter("newfile.txt"))) {
                for (String line : lines)
                    writer.write(line + "\n");
            } catch (IOException i) {
                System.out.println("Cannot write file...");
            }

            System.out.println("File saved!");
            System.exit(0);
        }
    });

当窗口关闭时，上面的代码将把修改后的文本保存到文件newfile.txt

在上面的例子中，拆分成行可能是不必要的；只需执行writer.write(theText.getText());即可获得正确的输出。不过，主要的收获应该是使用WindowAdapter

一些相关文件：

How to Write Window Listeners

Answer 2

下面是一个使用JButton触发事件来保存文本文件的示例

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import java.io.*;

public class DisplayPanel {

    public static String textFilePath = // adjust path as needed
            "C:\\Users\\Andrew\\Documents\\junk.txt";
    private JComponent ui = null;
    private JFrame frame;
    private JTextArea theText;
    private JButton saveButton;
    private ActionListener actionListener;
    File file;

    DisplayPanel(File file) {
        this.file = file;
        try {
            initUI();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    private void saveText() {
        Writer writer = null;
        try {
            writer = new FileWriter(file);
            theText.write(writer);
        } catch (IOException ex) {
            ex.printStackTrace();
        } finally {
            try {
                writer.close();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }

    public final void initUI() throws FileNotFoundException, IOException {
        if (ui != null) {
            return;
        }

        ui = new JPanel(new BorderLayout(4, 4));
        ui.setBorder(new EmptyBorder(4, 4, 4, 4));

        theText = new JTextArea(20, 120); //120 monospaced chrs
        theText.setFont(new Font(Font.MONOSPACED, Font.PLAIN, 14));
        theText.setLineWrap(true);
        theText.setEditable(true);
        JScrollPane scroll = new JScrollPane(theText);
        scroll.setVerticalScrollBarPolicy(
                ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

        ui.add(scroll);

        saveButton = new JButton("Save");
        ui.add(saveButton, BorderLayout.PAGE_START);

        actionListener = (ActionEvent e) -> {
            saveText();
        };
        saveButton.addActionListener(actionListener);

        Reader reader = new FileReader(file);
        theText.read(reader, file);
    }

    public void createAndShowGUI() {
        frame = new JFrame(this.getClass().getSimpleName());
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.setLocationByPlatform(true);

        frame.setContentPane(getUI());
        frame.pack();
        frame.setMinimumSize(frame.getSize());

        frame.setVisible(true);
    }

    public JComponent getUI() {
        return ui;
    }

    public static void main(String[] args) {
        Runnable r = () -> {
            try {
                UIManager.setLookAndFeel(
                        UIManager.getSystemLookAndFeelClassName());
            } catch (Exception useDefault) {
            }
            File file = new File(textFilePath);
            DisplayPanel o = new DisplayPanel(file);
            o.createAndShowGUI();
        };
        SwingUtilities.invokeLater(r);
    }
}